JPH11288624A - Electrical insulating composition and electric wire/cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrical insulating composition and electric wire/cable having excellent characteristics such that the rate of water tree formation is reduced, the dielectric breakdown voltage at high temperatures is high, and that the dielectric loss tangent is small. SOLUTION: This composition is obtained by blending 100 parts by weight of a polyethylene or ethylene copolymer and 0.02 to 50.0 parts by weight of an alkylphenylketone having a phenyl group and a ketone bond in its molecules. Alternatively, the composition is obtained by blending 100 parts by weight of the polyethylene or ethylene copolymer, an alkylphenylketone having a phenyl group and a ketone bond in its molecules, and an unsaturated dimer of α-aromatic substituent α-methylalkene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating composition and electric wires and cables.

[0002]

2. Description of the Related Art Polyolefins such as polyethylene and polypropylene are widely used as electrical insulating compositions for insulating coatings of electric wires and cables because they are hydrocarbon polymer materials having excellent electrical properties. In particular, so-called cross-linked polyethylene obtained by cross-linking polyethylene is widely used as an electrical insulating composition for insulating coating of high-voltage wires and cables because of its excellent heat resistance, which is a drawback of polyethylene.

[0003] However, high-voltage electric wires coated with cross-linked polyethylene
Trees have tree-like defects, i.e., water trees, in the coated cross-linked polyethylene layer when harsh conditions such as high voltage, high humidity or humidity, high temperature, etc. are applied over many months, and when the water trees are severe, It has been found that electrical breakdown occurs from the part.

[0004] The water tree of such cross-linked polyethylene is composed of voids in the cross-linked polyethylene layer, a small amount of foreign matter mixed in the cross-linked polyethylene layer, and amber in the cross-linked polyethylene layer (one having a high degree of polymerization, It is said that water aggregates at a defective portion of a local high electric field portion such as a partially high molecular weight by cross-linking, and the water tree grows through the aggregated water.

[0005] It should be noted that high-voltage electric wires with cross-linked polyethylene
Electrical breakdown of the cable under conditions where moisture does not participate,
Examination of the electrical breakdown point shows that the starting point of the dielectric breakdown is a minute amount of foreign matter mixed in the cross-linked polyethylene layer, an amber in the cross-linked polyethylene layer, or the like.

Accordingly, in order to suppress the occurrence of these defective portions, wire / cable manufacturers continuously improve the quality control of the raw material polyethylene and the technology for manufacturing the wires / cables, and as a result, the occurrence of water trees can be reduced. It is becoming.

However, the conventional electric insulating composition of a crosslinked polyethylene insulated wire or cable which has reduced the generation of water trees has a low electric breakdown voltage at high temperatures,
There was a disadvantage that the dielectric loss tangent increased.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned disadvantages of the prior art, to reduce the occurrence of water trees and to reduce the temperature under high temperatures. It is an object of the present invention to provide an electric insulating composition and an electric wire / cable having excellent characteristics such as a high electric breakdown voltage and a small dielectric loss tangent.

[0009]

The gist of the present invention lies in the following two points.

(1) An alkyl phenyl ketone having a phenyl group and a ketone bond in a molecule of 0.02 to 100 parts by weight of polyethylene or an ethylene copolymer is used.
An electric insulating composition characterized by being blended in an amount of up to 50.0 parts by weight, and an electric wire / cable coated with the same.

(2) With respect to 100 parts by weight of polyethylene or ethylene copolymer, unsaturated dimer of alkylphenyl ketone having a phenyl group and a ketone bond in the molecule and α-aromatic substituted α-methylalkene And an electric insulating composition, and an electric wire / cable coated with the same.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the electric insulating composition and the electric wires / cables of the present invention will be described.

In the present invention, the polyethylene or the ethylene copolymer may be those industrially practical.

Here, polyethylene includes low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene and the like. In addition, examples of the ethylene copolymer include an ethylene-propylene copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-vinyl acetate copolymer, and an ethylene-styrene copolymer. In the present invention, as the polyethylene or ethylene copolymer, those obtained by grafting maleic anhydride, vinylsilane, or the like thereto may be used. Further, two or more of these may be used in combination, and furthermore, these may be used alone or in combination.
Other compounding agents such as antioxidants, lubricants, coloring agents, etc. may be added to more than one kind.

The alkylphenyl ketone having a phenyl group and a ketone bond in the molecule used in the present invention includes n-octanophenone, n-decanophenone, laurophenone, n-tetradecanophenone and n-hexadecanophenone. N-heptadecanophenone, n-optadedecanophenone, 4'-n-octylacetophenone, 4-n-octanoylbiphenyl, 1,9-diphenyl-1,3,6,8-nonatetraen-5-one , 2
-Isopropoxy-1,2-diphenylethane and the like. These can be used alone or in combination of two or more.

In the present invention, the amount of the alkyl phenyl ketone is limited to 0.02 to 50.0 parts by weight per 100 parts by weight of polyethylene or ethylene copolymer. This is because the effect of reducing the bow titley is poor, and conversely, if the content is 50.0 parts by weight or more, the electrical characteristics rapidly deteriorate.

When the amount of the unsaturated dimer of α-aromatic substituted α-methylalkene is less than 0.05 part by weight, the effect of suppressing scorch is small, and when it is more than 0.05 part by weight, the electrical characteristics are sharp. This is because it becomes worse.

It is preferable that the electric insulating composition of the present invention is crosslinked after covering the electric wire / cable.

The means for crosslinking the electrically insulating composition includes crosslinking with a peroxide crosslinking agent, water crosslinking with a silane crosslinking agent, irradiation crosslinking by electron beam irradiation, and the like.

Here, the peroxide crosslinking agent is dicumyl peroxide, 1- (2-tert-butylperoxyisopropyl) -1-isopropylbenzene or 1- (2-tert-butylperoxyisopropyl).
-3-isopropylbenzene, 1,3-bis- (ter
t-butylperoxyisopropyl) benzene, 2.5
-Di (tert-butylperoxy) hexane, 2,5
-Dimethyl-2,5 (tert-butylperoxy)-
Hexin-3 and the like. These can be used alone or in combination of two or more.

These crosslinking agents are α-aromatic substituted α
When used in combination with an unsaturated dimer of -methyl alkene, scorch can be suppressed.

Such α-aromatic substituted α-methylalkenes include α-methylstyrene and para-methyl-α-
Methylstyrene, para-isopropyl-α-methylstyrene, meta-methyl-α-methylstyrene, meta-ethyl-α-methylstyrene, ar-dimethyl-α-methylstyrene, ar-chloro-α-methylstyrene, ar-
Chlor-ar-methyl-α-methylstyrene, ar-diethyl-α-methylstyrene, ar-methyl-ar-isopropyl-α-methylstyrene and the like.

Specific examples of such unsaturated dimers of α-aromatic substituted α-methylalkene include, for example, α
And 2,4-diphenyl-4-methyl-1-pentene which is an unsaturated dimer of methylstyrene.

In the present invention, in addition to these additives, other additives such as antioxidants, lubricants, coloring agents, fillers and the like can be added.

[0025]

EXAMPLES Next, examples of the electric insulating composition and electric wires / cables of the present invention will be described together with conventional comparative examples.

(1) Weighing and Sampling of Electrical Insulating Composition First, the electrical insulating compositions of Examples and Comparative Examples were weighed and collected according to the component table shown in the upper column of Table 1.

(2) Preparation of pellets of electrical insulating composition The electrical insulating compositions of Examples and Comparative Examples weighed and collected in the above (1) were kneaded with hot kneading rolls, respectively, to form sheets.

Next, the obtained sheets of the electrical insulating composition of the example and the comparative example were each subjected to a pelletizer to obtain pellets of the electrical insulating composition.

(3) Manufacture of cross-linked polyethylene insulated wire Next, an extruder is used to form an inner semiconductive layer having a thickness of 0.7 mm directly on a soft copper wire having a conductor cross section of 100 mm ² , and the above semiconductive layer is formed on the inner semiconductive layer. The polyethylene is obtained by extruding and coating in a single step a 0.7 mm-thick external semiconductive layer on the pellets of the electrical insulating compositions of the examples and comparative examples obtained in (2), and further on the electrical insulating composition layers. An insulated cable was obtained.

Next, the polyethylene insulated cables of Examples and Comparative Examples were passed through a dry cross-linking tube under a high-temperature nitrogen gas atmosphere to cross-link the polyethylene insulated layer. Got the cable.

FIG. 1 shows a cross-sectional view of the crosslinked polyethylene insulated cable of Example 1 thus obtained, wherein 1 is a conductor, 2 is an inner semiconductive layer, 3 is a crosslinked polyethylene insulating layer, and 4 is an outer half. It is a conductive layer.

(4) Evaluation test of crosslinked polyethylene insulated cable a. Measurement of AC Breakdown Voltage at High Temperature First, the cross-linked polyethylene insulated cables of Examples and Comparative Examples were heated to a temperature of 90 ° C., and the AC voltage was first increased to 170 kV.
For 10 minutes, and then stepwisely increased the voltage at a rate of 5 kv / 10 minutes to measure the electric breakdown voltage.

B. Bow Titlery Test First, the crosslinked polyethylene insulated cables of the Examples and Comparative Examples were each immersed in warm water at a temperature of 90 ° C., and an AC voltage of 50 Hz, 9 kv was applied between the conductor and the water,
500 days in that state.

Next, after 500 days, the cross-linked polyethylene insulated cables of Examples and Comparative Examples were sliced in cross section.

Next, the obtained crosslinked polyethylene insulating layer slice was immersed in an aqueous methylene blue solution, and then subjected to boiling dyeing treatment.

Next, the crosslinked polyethylene insulating layer slice thus dyed was observed with an optical microscope, and the cumulative number of bow title trees was counted.

[0037] c. Measurement of dielectric loss tangent The dielectric loss tangent of each of the crosslinked polyethylene insulated cables of Examples and Comparative Examples was measured under an electric field of 10 kv / mm.

The results are indicated by ○ when the dielectric loss tangent is 0.05% or less, and by X when the value is 0.05% or more.

(5) Test Results The test results are as shown in the lower column of Table 1.

[0040]

[Table 1]

(6) Evaluation of Test Results The crosslinked polyethylene insulated cable of Comparative Example 1 has the largest number of bow title trees and the worst tree resistance.

The crosslinked polyethylene insulated cable of Comparative Example 2 has a small number of bow title trees and a good tree resistance. However, the crosslinked polyethylene insulated cable of Comparative Example 2 had a low AC breakdown voltage at high temperatures and a poor dielectric loss tangent.

On the other hand, the crosslinked polyethylene insulated cables of Examples 1 to 5 have a small number of bow title trees, good tree resistance, high AC breakdown voltage at high temperature, and a dielectric loss tangent of ○. And all showed excellent results.

[0044]

Industrial Applicability The electrical insulating composition and electric wires and cables of the present invention have excellent tree resistance, high AC breakdown voltage at high temperatures, and a small dielectric loss tangent, and are industrially useful. It is.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a crosslinked polyethylene insulated cable according to a first embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 conductor 2 inner semiconductive layer 3 crosslinked polyethylene insulating layer 4 outer semiconductive layer

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 5/25 C09D 5/25 H01B 9/02 H01B 9/02 A (72) Inventor Ken Okuyama 5 Hidakacho, Hitachi City, Ibaraki Prefecture Chome 1-1 Hitachi Power Systems Co., Ltd. Power System Laboratory

Claims (5)

[Claims] 1. An alkyl phenyl ketone having a phenyl group and a ketone bond in a molecule of 0.02 to 5 parts by weight per 100 parts by weight of polyethylene or ethylene copolymer.
An electrical insulating composition comprising 0.0 parts by weight. 2. The method according to claim 1, wherein the alkylphenyl ketone is n-octanophenone, n-decanophenone, laurophenone, n-octanophenone.
Tetradecanophenone, n-hexadecanophenone, n
-Heptadecanophenone, n-optadecanophenone,
4'-n-octyl acetophenone, 4-n-octanoylbiphenyl, 1,9-diphenyl-1,3,6,8
-Nonatetraen-5-one, 2-isopropoxy-
2. The electrical insulating composition according to claim 1, wherein the composition is a mixture of at least one selected from 1,2-diphenylethane. 3. An unsaturated dimer of an alkyl phenyl ketone having a phenyl group and a ketone bond in the molecule and an α-aromatic substituted α-methyl alkene, based on 100 parts by weight of polyethylene or ethylene copolymer. An electrical insulating composition characterized by comprising: 4. An electric wire or cable in which an insulating layer is coated directly above a conductor or via a semiconductive layer, wherein the insulating layer is a phenyl group in a molecule with respect to 100 parts by weight of polyethylene or ethylene copolymer. A wire or cable comprising an electrical insulating composition containing 0.02 to 50.0 parts by weight of an alkylphenyl ketone having a ketone bond. 5. An electric wire or cable comprising an insulating layer coated directly on a conductor or via a semiconductive layer, wherein the insulating layer is a phenyl group in a molecule with respect to 100 parts by weight of polyethylene or ethylene copolymer. A wire or cable comprising an electrical insulating composition containing an alkyl phenyl ketone having an alkylphenyl ketone and a unsaturated dimer of α-aromatic substituted α-methylalkene.